PowerPoint is a decent tool for creating lightweight animations.

With the right use of tools like morph transition etc. one can achieve pretty decent looking or even professional looking animations of concepts.

I have also used PowerPoint to create web application wireframes, design concepts, Logos and website graphics, icons, repeating fill patterns, arbitrary vector graphics, etc.

I guess one strong point is how easily / widely available the tool is, and therefore even if you don't have the same machine with all your design tools, or don't have admin access to install them, you can still edit your work later easily.